- John I, King of Portugal, 1357-14331
- John VIII Palaeologus, Emperor of the East, 1392-14481
- John the Baptist's Day1
- Joseph Della Reina, active 15th century1
- Juana, of Austria, Princess of Portugal, 1535-15731
- Judgment Day (Islam)1
- Julius III, Pope, 1487-15551
- Jurjānī, ʻAlī ibn Muḥammad, al-Sayyid al-Sharīf, 1340-14131
- Jurjānī, ʻAlī ibn Muḥammad, al-Sayyid al-Sharīf, 1340-1413. Miṣbāḥ fī sharḥ al-Miftāḥ1
- Jurjānī, ʻAlī ibn Muḥammad, al-Sayyid al-Sharīf, 1340-1413. Sharḥ Farāʼiḍ al-Sirājīyah1
- Jāmiʻ al-ṣaḥīḥ (Muslim ibn al-Ḥajjāj al-Qushayrī)1
- Jārbardī, Fakhr al-Dīn Aḥmad ibn al-Ḥasan, d. 1345. Mughnī fī ʻilm al-naḥw1
- Kamāl al-Dīn Muḥammad ibn Muḥammad, -1418. Naẓm Nukhbat al-fikar fī muṣṭalaḥ ahl al-athar1
- Karma1
- Kashshāf (Zamakhsharī, Maḥmūd ibn ʻUmar)1
- Kaydānī. Maṭālib al-muṣallī1
- Kemalpaşazade, 1468 or 1469-1534. Īḍāḥ al-iṣlāḥ1
- Khalifa ben Shemuʹel, 17th century1
- Khalwatīyah1
- Khamrīyah (Ibn al-Fāriḍ, ʻUmar ibn ʻAlī)1